What is Sunscreen?

Sunscreen protects the skin from absorbing ultraviolet (UV) rays. Sunscreen products contain one or more UV filters as active ingredients. There are two kinds of UV rays that can affect the skin: UVA and UVB. In the U.S., sunscreen is considered an over-the-counter drug and is regulated by the U.S. Food and Drug Administration.

The preventive benefit of sunscreen was clearly demonstrated in a large Australian randomized trial published in 2010, which showed a 50% decreased melanoma risk by using sunscreen regularly. This study was critical evidence not only for Australia, which has the highest melanoma rate in the world (along with New Zealand), but for all countries. Sunscreen works.

Two Types of Sunscreen

Sunscreen filters can be broadly classified into two groups: mineral and organic.

Mineral Filters

Mineral filters—sometimes called inorganic or physical—work by deflecting or scattering UV light, preventing the UV light from hitting your skin. They are effective at protecting against both UVA and UVB radiation. They are not readily absorbed into your skin. Sunscreens with mineral filters begin to work as soon as they are applied to the skin.  The two mineral filters used in U.S. sunscreen are zinc oxide and titanium dioxide.

Organic Filters

Sunscreens with organic—sometimes called chemical—filters work by absorbing UV light. They allow the UV light to hit the skin but transform it into a non-harmful wavelength of light. Unlike physical blockers, organic sunscreens do absorb into the skin. They take about 15 minutes to absorb, so they should be applied 15 minutes prior to any sun exposure in order to work effectively. They often contain multiple organic filters. The filters can be differentiated by the type of rays they absorb: UVA, UVB, or both UVA and UVB. The six organic filters typically used in U.S. sunscreens are avobenzone, homosalate, octinoxate, octisalate, octocrylene, and oxybenzone.

Combination Sunscreens

Some sunscreens are a combination of organic and mineral filters.

Broad Spectrum Sunscreens

Per FDA regulations, sunscreen can only be called “broad spectrum” if it protects against both UVA and UVB. Most U.S. sunscreens combine two or three of the above eight filters to get the best performance. Importantly, only three of these filters—oxybenzone, avobenzone, and zinc oxide—work in the UVA range. While the FDA has approved 16 sunscreen filters for use in the U.S., these eight are most commonly used.

What Does SPF Stand For?

SPF stands for Sun Protection Factor and refers to the level of sunburn protection provided by the sunscreen product. All sunscreens are tested to measure the amount of UV radiation exposure it takes to cause sunburn when using a sunscreen vs. when not using a sunscreen. The higher the SPF, the greater the protection is from UV radiation, and the greater the sunburn protection. Most people assume that SPF relates to a timeframe of protection. For example, it’s a common belief that an SPF of 30 would theoretically allow you to stay in the sun 30 times longer than you could without protection. But the FDA reminds us that the amount of UV exposure isn’t the same as the amount of time spent in the sun. Why? Because radiation exposure is greater at 1 pm than 9 am; greater in Florida than in North Dakota; and greater in summer than in winter. Additionally, your actions affect the amount of UV exposure you receive: You may not apply enough sunscreen, or you may miss areas; you may swim or sweat, which removes sunscreen; your towel or clothing may rub sunscreen off. In all cases, sunscreens are effective for no more than two hours—and all of the above circumstances contribute to how much UV exposure you will receive.

AIM recommends that you use a broad-spectrum sunscreen of SPF 30 or higher daily on all exposed skin and reapply it at least every two hours, as well as after swimming, sweating, or towel drying.

Because SPF values are determined from a test that measures protection against sunburn caused by UVB radiation, SPF values only indicate a sunscreen’s protection from UVB—the kind of radiation that causes sunburn, damages the skin, and can contribute to developing melanoma.

Currently, there is no internationally agreed-upon test for measuring UVA protection in human skin. An estimate is made by a laboratory test in which the proportion of radiation passing through a measured amount of sunscreen is determined.

Here’s how your sun protection looks with each level of SPF:
SPF 15 – filters about 93% of UVB rays
SPF 30 – filters about 97% of UVB rays
SPF 50 – filters about 98% of UVB rays
SPF 100 – filters about 99% of UVB rays

To get the most protection, you want a broad-spectrum sunscreen—these protect against UVB and UVA rays. UVA rays are long enough to reach the skin’s dermal layer, damaging collagen, and elastic tissue. That layer is also where the cells that stimulate skin darkening are found; that’s why UVA rays are considered the dominant tanning rays. (UVA rays are what is found in tanning beds and other tanning devices.) Though many people still think a tan looks healthy, it’s actually a sign of DNA damage—the skin darkens in an imperfect attempt to prevent further injury, which can lead to the cell mutations that can lead to melanoma.

Sunscreen should be just one of the sun protection strategies you use to protect your skin. You also need to cover up with clothing and a hat, seek shade, and try to stay out of the sun during peak hours, which are from 10:00 am to 4:00 pm.

 

Applying Sunscreen Correctly 

Apply enough sunscreen to cover all exposed skin. Most adults need about one ounce — the amount in a shot glass — for full-body protection. Don’t forget to apply it to your ears, hands, feet, the back of your neck and any part of your scalp that isn’t covered by hair. Make sure to apply to the underside of your chin, which can be exposed to reflected sunlight. Remember: Most people don’t apply enough sunscreen, so it’s okay to use more than you think you should. Many people wait to put on sunscreen when already outside, but you should apply it before you go in the sun if you use organic sunscreens, which need approximately 15 minutes to absorb into your skin and begin working. And don’t forget to wear sunscreen even on cloudy days and during the winter months. UV rays can still harm your skin when it’s cloudy outside. Finally, check the expiration date on your sunscreen to make sure it is not out of date. If your sunscreen changes consistency, becomes watery, separates, or changes color, even if it has not expired, it should be discarded. Sunscreen should not be left in direct sunlight or a hot environment like a car, as the heat can break down the chemicals in the sunscreen.

No Sunscreen is Waterproof or Sweatproof 


Manufacturers of sunscreen cannot make claims that sunscreens are “waterproof” or “sweatproof.” Instead, sunscreen labels may say “water-resistant” and must specify whether they protect the skin for 40 or 80 minutes of swimming or sweating based on standard testing, according to the FDA. Always reapply sunscreen immediately after swimming, sweating, or toweling.

 

 

When To Reapply


Reapply one ounce of sunscreen at least every two hours, even if you haven’t been sweating or swimming. Cover all of your skin that will be exposed to the sun, including often neglected areas like your back, your ears, and behind your knees.

 

 

Keep Babies Out of the Sun 

Sunscreen may be used on babies older than six months, but the skin on a baby is less mature compared to adults, and infants have a higher surface-area to body-weight ratio compared to older children and adults. Therefore, babies need to be physically protected by keeping them out of the sun and in the shade as much as possible. If there’s no natural shade, create your own with an umbrella, pop-up tent, or the canopy of the stroller. Make sure your baby wears a hat that provides sufficient shade at all times and clothing that covers and protects sensitive skin. Consult your pediatrician before using any sunscreen on your baby.

Why Has Sunscreen Been in the News Lately?

There are at least three reasons you might have read about sunscreen in the news over the last few years.

Reason #1

One newsworthy item is whether some organic filters are systemically absorbed in the body after application and, if so, whether there is any danger to the consumer.

In January 2020, the Journal of the American Medical Association reported the results of a study (a follow-up to a previous study) to assess whether, and to what extent, certain organic sunscreen ingredients are absorbed into the body through the skin. This study tested six organic sunscreen filters—avobenzone, homosalate, octinoxate, octisalate, octocrylene, and oxybenzone—in four different formulations to analyze the ingredients’ absorption levels in the blood.

Janet Woodcock of the FDA said, when announcing the study, “Results from our study released today show there is evidence that some sunscreen active ingredients may be absorbed. However, the fact that an ingredient is absorbed through the skin and into the body does not mean that the ingredient is unsafe, nor does the FDA seeking further information indicate such. Rather, this finding calls for further industry testing to determine the safety and effect of systemic exposure of sunscreen ingredients, especially with chronic use” (italics added).

And she stated clearly: “The FDA urges Americans to use sunscreens in conjunction with other sun-protective measures (such as protective clothing).”

Reason #2

Sunscreen has also been in the news because of claims that some organic filters may damage the marine environment, specifically coral reefs.

Hawaii has banned oxybenzone and octinoxate, two ingredients found in many organic sunscreens.

A few years ago, there was a flurry of media reports about studies that connected several organic sunscreen ingredients to reef damage such as slowing coral growth and increasing the rate of coral bleaching. In 2018, the International Coral Reef Initiative came out with a review of studies related to sunscreen and coral reefs called Impacts of Sunscreens on Coral Reefs. The finding was that “further research is needed to better understand which ingredients are safe and which pose a realistic threat to marine ecosystems,” but that oxybenzone “has been identified as the main substance of concern.”

The report concluded that further research is needed because “there is a lack of firm evidence of widespread negative impacts at reef community and/or ecosystem level. The evidence available may not properly reflect conditions on the reef, where pollutants may rapidly disperse and be diluted.”

The U.S. Congress is aware of the data gaps and has directed the EPA to work with the National Academy of Sciences to “conduct a review of the scientific literature of currently marketed sunscreens’ potential risks to the marine environment…and the current scientific literature on the potential public health implications associated with reduced use of currently marketed sunscreen ingredients for protection against excess ultraviolet radiation.”

Reason #3

Sunscreen has also been in the news because of “new” UV filters available in Europe but not in the U.S.

The next generation of photostable, broad-spectrum sunscreens that offer UVA and UVB protection has long been approved for use in European and other countries, but not yet in the U.S. There are eight “new” sunscreen filter applications awaiting approval from the FDA, and those applications were filed between 2002 and 2009.

The FDA has said they need more data on these filters. AIM hopes for approval soon because approval of any or all the ingredients would help consumers have access to a larger selection of sunscreens. Additionally, many in the melanoma world say several of these new filters are superior to what we have in the U.S., so approval means both a larger selection AND better protection from UV rays. That’s a win-win for consumers.

The bottom line with these sunscreen questions is that more research is needed to answer certain questions, but more research is not a reason to stop wearing sunscreen. Research is clear that UV rays are a major risk factor for skin cancer; skin cancer is the most common cancer in the U.S.; and melanoma is the deadliest form of skin cancer. Sunscreen is an important way to reduce the risk of developing skin cancers, including melanoma. If any information on a UV filter concerns you, choose a product with a different filter. But continue to protect your skin!

2022 Update: The State of Sunscreen in the U.S.